Color display apparatus

ABSTRACT

This invention provides a display apparatus having high accuracy to control automatically power consumed for display operation suitable for emission-type display apparatus like a plasma display apparatus, electroluminescence display apparatus and a light emission diode display apparatus. The display apparatus comprises an emission unit ( 27 ), integrating circuits ( 11,12,13 ) for integrating input picture signals of R, G and B for each predetermined period to output average levels of R signal, G signal and B signal, respectively, multiplying circuits ( 14,15,16 ) for multiplying those average levels by their respective parameters KR, KG and KB, respectively, an adder ( 17 ) for obtaining a signal indicating expected consumption power on the emission unit by adding output signals from the multiplying circuits, a controller ( 18 ) for receiving the power prediction signal to output a control signal based on the received signal, and a brightness control circuit for controlling light emission amount per unit area according to the control signal.

TECHNICAL FIELD

The present invention relates to display apparatuses such as plasmadisplays, electroluminescence displays, and light emitting diodedisplays.

BACKGROUND ART

Conventionally, a light-emitting type display apparatus such as a plasmadisplay, an electroluminescence display or a light emitting diodedisplay generally emits light to display when it has some amount ofinformation that should be displayed. The display apparatus inevitablyinvolves large power consumption as the amount of information to bedisplayed becomes large. Therefore, it has been studied to restrictpower consumption when the amount of display data has become large. InJapanese Patent Laid-Open Publication No. H08-65607, it is disclosedthat depending on average luminance signal level of images, an automaticpower control (APC) section adjusts the light emission amount per unitarea (luminance) of a display in response to variations in the averageluminance signal level so that the power consumption is controlled so asnot to increase excessively.

FIG. 11 is a block diagram showing the configuration of the displayapparatus according to the prior art disclosed in the publication. R, Gand B signals as picture signals are fed into their correspondingterminals. The R, G and B signals via their corresponding terminals arefed into a Y-encode circuit 61 which encodes the R, G and B signals intoa luminance signal (hereinafter, referred to as Y signal) to output. Adigital luminance integrating circuit 62 inputs and integrates the Ysignal from the Y-encode circuit 61 to output an average luminance.

Taking as a parameter the average luminance outputted from the digitalluminance integrating circuit 62, a memory controller 63 receives datacorresponding to the average luminance from a memory 64 to output thedata to an automatic power controller 66 of a plasma display apparatus68. The automatic power controller 66 outputs to a PDP (plasma displaypanel) display section 67 a control signal for adjusting the lightemission amount per unit area (luminance) of the PDP display section 67in response to the data from the memory control section 63, therebypower consumption is controlled.

However, the power consumption at the PDP display section 67 is notproportional to the luminance signal. For example, with a commontransform equation, Y=0.3R+0.59G+0.11B, used in the Y-encode circuit 61,the ratio among their respective luminance signals (YR, a luminancesignal for display of single red; YG, a luminance signal for display ofsingle green; and YB, a luminance signal for display of single blue) isYR: YG: YB =0.3:0.59:0.11 when single color of red (hereinafter,expressed as R), green (hereinafter, expressed as G) and blue(hereinafter, expressed as B) are displayed,. Here, the luminance signalYG for the display of G is the largest and the luminance signal YB forthe display of B is the smallest so that different control processes areperformed by the automatic power controller 66 for the respective casesof the display of the single color depending on the average luminance.Ratio among respective coefficients (0.3, 0.59,0.11) for obtainingluminance signals in the transform equation equals to a ratio at whichhuman eyes feel the brightness with each three primary colors (R, G, B),and do not show any power consumption ratio. Therefore, it may causeinappropriate control to be performed.

As shown above, in the technique of the prior art, with averageluminance used as a parameter for the power consumption control of adisplay apparatus, light emission amount (luminance) of the displaysection 67 would be recognized as less than required amount in the caseof an image in which green components occupy a larger portion than theother colors, and power consumption would be recognized as more than theperformance of the power supply 65 in the case of an image in which bluecomponents occupy a larger portion than the other colors. Thus, it hasbeen a problem of the prior art technique that an accurate automaticcontrol of power consumption or light emission amount cannot beachieved.

DISCLOSURE OF THE INVENTION

In order to solve the above problem, a display apparatus of the presentinvention is characterized in that the light emission amount (luminance)or power consumption is controlled based on a power prediction signalobtained by weighted average levels of individual colors withcoefficients representing ratios of power consumptions involved in datadisplay when the three primary colors of red, green and blue aredisplayed in single colors, respectively, or representing ratios ofphosphor areas of the individual colors, and by then summing up theweighted average levels.

According to the present invention, since the power consumption or lightemission amount (luminance) is controlled based on a power predictionsignal computed with coefficients representing power consumption ratiosor phosphor area ratios, it becomes possible to control the powerconsumption or light emission amount (luminance) independently of thehue of input picture signals.

In a first aspect of the invention, a display apparatus comprises anemission unit, integrating circuits, three multiplying circuits, a powerconsumption prediction circuit, a controller and a brightness controlcircuit.

The emission unit emits light to display images. The integratingcircuits integrate input picture signals of R (red), G (green) and B(blue) for each predetermined period to output an average level of Rsignal, an average level of G signal and an average level of B signal,respectively. The first, second and third multiplying circuitsmultiplies the R average level, the G average level and the B averagelevel by their respective parameters KR, KG and KB, respectively. Thepower prediction circuit adds output signals from those multiplyingcircuits together to obtain and output a power prediction signal. Thesignal indicates amount of power predicted or expected to be consumed onthe emission unit. The controller receives the power prediction signalto output a control signal based on a value of the received signal. Thebrightness control circuit controls light emission amount per unit areaaccording to the control signal.

In the display apparatus, a ratio of parameters KR, KG and KB may bedetermined to be equal to a ratio of powers consumed for display eachcolor of red, green and blue with same brightness. In this case, thedisplay apparatus can control the power consumption or light emissionamount (luminance) more accurately, as compared with the prior arttechnique in which power consumption of the display apparatus iscontrolled with average luminance.

In a second aspect of the invention, a display apparatus comprises anemission unit, integrating circuits, first, second and third multiplyingcircuits, a power consumption prediction circuit, a controller, a delaycircuit and a first, second and third multiplying circuits.

The emission unit emits light to display images. The integratingcircuits integrates input picture signals of R, G and B for eachpredetermined period to output an average level of R signal, an averagelevel of G signal and an average level of B signal, respectively. Thefirst, second and third multiplying circuits multiplies the R averagelevel, the G average level and the B average level by their respectiveparameters KR, KG and KB, respectively. The ratio of parameters KR, KGand KB is determined to be equal to a ratio of powers consumed fordisplay each color of red, green and blue with same brightness. Thepower consumption prediction circuit adds output signals from themultiplying circuits together to obtain and output a power predictionsignal. The signal indicates amount of power expected to be consumed onthe emission unit. The controller receives the power prediction signalto output a multiplying coefficient based on a value of the receivedsignal. The delay circuit delays the input picture signals of R, G and Bto output the delayed picture signals DR, DG and DB, respectively. Thefourth, fifth and sixth multiplying circuits multiplies the delayedpicture signals DR, DG and DB by the multiplying coefficient,respectively.

In a third aspect of the invention, a display apparatus for dividing onefield of picture signal into a plurality of subfields weightedrespectively, and then displaying images of subfields in superimpositionon time region to realize gradation expression.

The display apparatus comprises an emission unit, R, G and B integratingcircuits, multiplying circuits, a power consumption prediction circuit,a controller, a delay circuit, picture signal-subfield associatingcircuit, a subfield pulse generator.

The emission unit emits light to display images. The R integratingcircuit, G integrating circuit and B integrating circuit integrates atleast one field of input picture signals of R, G and B to output anaverage level of R signal, an average level of G signal and an averagelevel of B signal, respectively. The multiplying circuits multiplies theR average level signal, the G average level signal and the B averagelevel signal by parameters KR, KG and KB determined based on the ratioof powers consumed for display each color of red, green and blue. Thepower consumption prediction circuit adds output signals from the first,second and third multiplying circuits together to obtain and output apower prediction signal. The signal indicates power expected to beconsumed on the emission unit. The controller receives the powerprediction signal to output a emission pulse control signal forselecting one of light emission types in response to a value of thereceived signal. The delay circuit for delaying the input picturesignals R, G and B to output the delayed picture signals DR, DG and DB,respectively. The picture signal-subfield associating circuit receivesthe emission pulse control signal and the delayed picture signals DR, DGand DB, and associates output signals from the delay circuit withsubfield structure of the light emission type based on the emissionpulse control signal. The subfield pulse generator receives the emissionpulse control signal, and generates pulses in the subfield structurecorresponding to the light emission type based on the emission pulsecontrol signal. The pulses include at least one of scanning pulses,sustaining pulses and erasing pulses.

In a forth aspect of the invention, a display apparatus for displayingimages of subfields in superimposition on time region to display datawith gradation, by dividing one field of picture signal into a pluralityof subfields weighted.

The display apparatus comprises an emission unit, R, G and B integratingcircuits, first, second and third multiplying circuits, a powerconsumption prediction circuit, a controller, a delay circuit, forth,fifth and sixth multiplying circuits, a picture signal-subfieldassociating circuit, a subfield pulse generator.

The emission unit emits light to display images. The R integratingcircuit, G integrating circuit and B integrating circuit integrates atleast one field of input picture signals of R, G and B to output an Raverage level signal, a G average level signal and a B average levelsignal, respectively. The multiplying circuits multiplies the R averagelevel signal, the G average level signal and the B average level signalby respective parameters KR, KG and KB obtained by a ratio of powersconsumed for display each color of red, green or blue. The powerconsumption prediction circuit adds output signals from the multiplyingcircuits together to obtain and output a power prediction signal. Thesignal indicates power expected to be consumed on the emission unit. Thecontroller receives the power prediction signal to output a emissionpulse control signal and a multiplying coefficient according to a valueof the received signal. The emission pulse control signal is availablefor selecting one of light emission types, the multiplying coefficientis available for equalizing gray scale level at a border of adjacentemission types. The multiplying coefficient is obtained based on thepower prediction signal from the controller. The delay circuit delaysthe input picture signals of R, G and B to output delayed picturesignals DR, DG and DB, respectively. The fourth, fifth and sixthmultiplying circuits multiplies the delayed picture signals DR, DG andDB by a multiplying coefficient for collecting gray scale level so as toequalize gray scale level between adjacent emission types at changeoverpoint of those emission types, respectively. The picture signal-subfieldassociating circuit receives the emission pulse control signal and thesignals of the fourth, fifth and sixth multiplying circuits as inputs,and associates the received signals from the fourth, fifth and sixthmultiplying circuits with subfield structure of a light emission typeresponsive to the emission pulse control signal. The subfield pulsegenerator receives the emission pulse control signal, and generatespulses including scanning, sustaining, erasing pulses with the subfieldstructure of a light emission type responsive to the emission pulsecontrol signal.

In the display apparatus described above, a ratio of the parameters KR,KG and KB may be equal to a ratio of area of phosphors for each color ofred, green and blue. Since the areas of the phosphors are generallyproportional to the power consumption, the power prediction signal canbe estimated in a simplified manner by weighting the individual coloraverage levels with coefficients representing the area ratios of thephosphors and then summing up the weighted average levels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of a displayapparatus of a preferred embodiment of the present invention.

FIG. 2 is a view showing light emission types of the display apparatus.

FIG. 3 is a view showing a relation between the power prediction signaland the actual consumption power when gradation correction is notperformed by the multiplying coefficient.

FIG. 4 is a view explaining operation for selection of light emissiontype by the controller.

FIG. 5 is a view showing a relation between the power prediction signaland the multiplying coefficient in the display apparatus.

FIG. 6 is a view showing a relation between the power prediction signaland the actual consumption power when gradation correction is performedby the multiplying coefficient (first multiplying coefficient).

FIG. 7 is a view showing a relation between the power prediction signaland the another multiplying coefficient (second multiplyingcoefficient).

FIG. 8 is a view showing a relation between the power prediction signaland the actual consumption power when gradation correction is performedby the second multiplying coefficient.

FIG. 9 is a view showing a control characteristic between the powerprediction signal of the display apparatus and the light emission amountper unit area (luminance) of the display apparatus.

FIGS. 10A and 10B are views showing the arrangement of phosphors of aplasma display panel which is an embodiment of the present invention;and

FIG. 11 is a block diagram showing the configuration of a displayapparatus according to the prior art.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to accompanied drawings, preferred embodiments of the presentinvention are described.

(Embodiment 1)

FIG. 1 is a block diagram showing an embodiment of the display apparatusaccording to the present invention. The display apparatus includes R Gand B integrating circuits. 11, 12 and 13, first, second and thirdmultiplying circuits 14, 15 and 16, an adder 17, a controller 18, adelay circuit 19, fourth, fifth and sixth multiplying circuits 20, 21and 22, a picture signal-subfield associating circuit 23, a subfieldpulse generator 24, a scan driver 25, a data driver 26 and a PDP (PlasmaDisplay Panel) 27.

The R integrating circuit 11, the G integrating circuit 12 and the Bintegrating circuit 13 receive an R signal, a G signal and a B signal astheir input picture signals, respectively, and produce output values asan R average level, a G average level and a B average level resultingfrom integrating those signals of a specific period, for example atleast one field, and then dividing integration results by the number ofintegration pixels.

R average level, G average level and B average level, are inputted to afirst multiplying circuit 14, a second multiplying circuit 15 and athird multiplying circuit 16, respectively, where the average levels aremultiplied by individual coefficients, KR, KG and KB, respectively, andthe results are outputted to the adder 17. The coefficients KR, KG andKB are defined such that ratio of those coefficients is equal to ratioof consumed power among R, G and B colors required for displaying datawith a single color respectively. That is, picture signals with sameconditions are inputted for R, G and B signal, respectively, withoutoperation of the controller 18, and consumed power required fordisplaying data in the PDP 27 with respective color is measured. Then,the ratio of coefficients KR, KG and KB are set to the ratio of thosemeasured powers for each color.

For example, the coefficients KR, KG and KB may be determined to have aratio such as KR:KG:KB=PR:PG:PB, where PR is consumed power required fordisplaying an image with a single color of red, PG is consumed powerrequired for displaying the image with a single color of green, PB isconsumed power required for displaying the image with a single color ofblue in the PDP 27.

The first multiplying circuit 14 multiplies the R average level by thecoefficient KR, the second multiplying circuit 15 multiplies the Gaverage level by the coefficient KG, and the third multiplying circuit16 multiplies the B average level by the coefficient KB. The adder 17adds up output signals from the first multiplying circuit 14, the secondmultiplying circuit 15 and the third multiplying circuit 16 to obtainand output a power prediction signal which indicates amount of powerexpected to be consumed on the PDP 27. The controller 18 inputs thepower prediction signal, selects one of light emission types to adjustthe light emission amount per unit area (luminance) of the displayapparatus so as to limit power consumption, and outputs emission pulsecontrol signal corresponding to the selected light emission type.Simultaneously, the controller 18 also outputs a multiplying coefficientby which the light emission amount (luminance) of an image does notdiffer at bounds of light emission types. The operation of thecontroller 18 is described in detail below.

The delay circuit 19 inputs the input picture signals R, G and B,produces picture signals DR, DG and DB which are delayed by a total timerequired at the individual sections of the integrating circuits 11, 12and 13, the multiplying circuits 14 to 16, the adder 17 and thecontroller 18 to output. The forth, fifth and sixth multiplying circuits20, 21 and 22 input the delayed picture signals DR, DG and DB,respectively, and multiply the delayed picture signals DR, DG and DB bythe multiplying coefficient from the controller 18 to output.

The picture signal-subfield associating circuit 23 inputs signals fromthe fourth, fifth and sixth multiplying circuits 20, 21 and 22 as wellas the emission pulse control signal. The picture signal-subfieldassociating circuit 23 converts the signals from the fourth, fifth andsixth multiplying circuits 20, 21 and 22 expressed in powers of 2 intolight-emission patterns of subfields of the light emission typecorresponding to the emission pulse control signal and then transmitsdata of the first subfield, data of the second subfield, and the data ofthe n-th subfield of each pixel in sequence during a one-field period atspecified timing (where n is the number of subfields). It is noted thatseveral operations, such as operation for changing the number ofsubfields to suppress the pseudo-contour noise, may be performed in thepicture signal-subfield associating circuit 23.

The subfield pulse generator 24 inputs the emission pulse controlsignal, and supplies a scanning sustaining and erasing signals withsubfield structure of the light emission type corresponding to theemission pulse control signal to the scan driver 25. The scan driver 25supplies scanning, sustaining and erasing signals to row electrodes of aPDP 27 at specified voltage level.

The data driver 26 inputs the output signal of the picturesignal-subfield associating circuit 23, generates image data pulses,each of which has voltage corresponding to individual pixel data, anddivides these pulses by columns to supply them to column electrodes ofPDP 27 in synchronism with signals outputted from the scan driver 25.Thus PDP 27 is driven to display images according to the input picturesignals.

In this preferred embodiment, when consumed power to display increasesaccording to increase of amount of information to be displayed by changeof input picture signal, light emission amount and brightness in theapparatus are controlled to limit consumed power within predeterminedrange. Specifically, light emission type (emission period and number ofemission) and gradation of the brightness in the display apparatus iscontrolled such that consumed power to display does not become largerthan a predetermined value P. For this purpose, the display apparatusexpects the consumed power based on the input picture signals, and thencontrols the emission type (emission period and number of times ofemission) and gradation (or gray scale) based on the expected consumedpower such that the consumed power is limited to be in a predeterminedrange.

In more detail, the controller 18 selects a light emission type inresponse to the power prediction signal and outputs an emission pulsecontrol signal for controlling the light emission type (emission timeduration or number of times of emission), as well as multiplyingcoefficients for adjustment of the gray scale level (or gradation level)of an input picture signal so that the light emission amount orluminance transits smoothly in the display apparatus between adjacentlight emission types.

The determination of the light emission type and the multiplyingcoefficients in the controller 18 is described below.

The emission type is firstly explained. As shown in FIG. 2, the displayapparatus of this embodiment has five emission types including emissiontype A, emission type B, emission type C, emission type D and emissiontype E, which decrease in the total number of times of light emission as1275, 1020, 765, 510 and 255, respectively, as the power predictionsignal increases in value.

On the basis of 8-bit gray scale levels ranging from 0 to 25.5, thenumber of emission pulses is so set that the number of times of lightemission is fivefold larger than the gray scale levels in the emissiontype A, fourfold larger than the gray scale levels in the emission typeB, and likewise threefold, twofold and one-fold larger than the grayscale levels in the emission type C, emission type D and emission typeE, respectively.

These emission types are changed over based on the power predictionsignal. The value (changeover point) of the power prediction signalwhich causes changeover of the emission type is described below. FIG. 3explains the determination of changeover points of the light emissiontype. The figure shows the relation between the power prediction signaland the consumed power for display. As shown in this figure, theemission type A and the emission type B are changed over .at thepredetermined value TB. The emission type B and the emission type C arechanged over at the predetermined value TC. The emission type C and theemission type D are changed over at the predetermined value TD. Theemission type D and the emission type E are changed over at thepredetermined value TE. The value TE, for example, is obtained asfollows. The consumed power is measured according to the vary of theinput picture signal which varies to reduce the power prediction signalgradually from the maximum value of the signal. It is noted that thepower prediction signal is obtained under the condition that themultiplying coefficient is 1. The consumed power decreases according tothe decrease of the power prediction signal. The changeover point TE isdetermined at the point where the consumed power is equal to thepredetermined value P.

The consumed power becomes 2P for the light emission with the powerprediction signal which is TE and the emission type which is D, becausethe number of times of emission type D is two times of that of emissiontype E. While the power prediction signal is decreased gradually fromthis point TE as a start point, the value at which the consumed powerreaches P is obtained as the power prediction signal value TD. Theexchange points TC and TB are determined respectively in like manner.

FIG. 4 is a flowchart of showing the operation of the controller 18which determines the emission type based on the power prediction signal.As shown in FIG. 4, firstly, the power prediction signal is compared tothe predetermined value TB (S1). When the signal is smaller than thevalue TB, the emission type A is selected (S6). When the signal is notsmaller than the value TB, the signal is compared to the predeterminedvalue TC (S2). When the signal is smaller than the value TC, theemission type B is selected (S7). When the signal is not smaller thanthe value TC, the signal is compared to the predetermined value TD (S3).When the signal is smaller than the value TD, the emission type C isselected (S8). When the signal is not smaller than the value TD, thesignal is compared to the predetermined value TE (S4). When the signalis smaller than the value TE, the emission type D is selected (S9). Whenthe signal is not smaller than the value TE, the emission type E isselected (S5).

When only changeovers among emission types having different numbers oftimes of light emission are performed on signals of the same gray scalelevel, the difference in number of times of light emission is detectedas a luminance difference in the display apparatus at a changeover ofemission type. Thus it needs to adjust the gray scale level of an inputpicture signal. Furthermore, as shown in FIG. 3, the consumed power fordisplaying data is greatly over the value P. Therefore, the controller18 outputs the multiplying coefficients varying in response to the powerprediction signal, and then the gray scale level to be actuallydisplayed is corrected by multiplying the input picture signals by themultiplying coefficients.

For example, when the power prediction signal is changed so that theemission type is changed over from emission type A to B, the followingrelation for same gray scale level is obtained as follows;

(luminance in emission type A): (luminance in emission type B)=(numberof times of emission in emission type A) (number of times of emission inemission type B)=5:4.

Therefore, the multiplying coefficient in the emission type A is so setas to be 1 for a small value of the power prediction signal. It is alsoso set as to monotonously decrease with increasing the power predictionsignal, and be 4/5=0.8 at a region adjacent to the region of theemission type B. For example, when the gray scale level of the inputpicture signal is 200, at the border between type A and type B, the grayscale level by the emission type A adjacent to the region of theemission type B is (200×0.8), which results in a number of times oflight emission, (200×0.8)×5=800, while the number of times of lightemission in the emission type B adjacent to the emission type A is200×4=800. Thus, the luminance in a display section 22 can be made equalbetween the two emission types.

As to the changes in the other emission types as well, with the sameconcept, the multiplying coefficients are so set as to be from 1 to 0.75(¾) in the emission type B, 1 to 0.67 (⅔) in the emission type C, andthe like as the power prediction signal increases in value. Bydetermining the multiplying coefficients like this, it is possible tocontrol gray scale level in display apparatus to allow luminancedifference not to be detected even though the emission type is changedover.

For example, when TB=0.2, TC=0.4, TD=0.6 and TE=0.8, the powerprediction signal value x and the multiplying coefficient y are obtainedas follows;

emission type A: y=−x+1(x<0.2)  (1)

emission type B: y=−5/4x+5/4(0.2<=x<0.2)  (2)

emission type C: y=−5/3x+5/3(0.4<=x<0.6)  (3)

emission type D: y=−5/2x+5/2(0.6<=x<0.8)  (4)

emission type E: y=ax+(1−0.8a)(0.8<=x)  (5).

When x>=0.8, that is, emission type is E, the multiplying coefficient yis 1.0 with x=0.8. The constant “a” is set not to be larger than zero sothat the multiplying coefficient y decreases as the power predictionsignal x increases, and to be any value which limits the consumed powerto the predetermined value P. For example, when x=0. 15 and the emissiontype A is selected, the multiplying coefficient is calculated asfollows;

Y=−x+1=−0.15+1=0.85.

FIG. 5 shows the change of the multiplying coefficient to the powerprediction signal by calculating the multiplying coefficient in a manneras described above.

When the multiplying coefficient is obtained based on the powerprediction signal in a manner as described above in the controller 18,the change of the consumed power to the power prediction signal has, acharacteristic as shown in FIG. 6 instead of one as shown in FIG. 3.Therefore, not depending on the input picture signal, the consumed powerfor data display is limited not so as to be over the predetermined valueP.

The multiplying coefficient may be changed curvilinearly in apredetermined interval as shown in FIG. 7, while it is changed linearlyas shown in FIG. 5. This can improve the characteristic of the consumedpower, where the consumed power is further limited to the value P asshown in FIG. 8.

The controller 18 determines these data (emission pulse control signaland multiplying coefficient) in correspondence to the value of the powerprediction signal. Specifically, the number of times of light emissionand the light emission time duration are decreased, or the multiplyingcircuit coefficient by which the delayed picture signals is multipliedis decreased, with increasing the power prediction signal, thereby thegray scale level of a signal to be displayed in the display apparatus isdecreased as compared with the gray scale level of the input picturesignal. Thus, the light emission amount per unit area (luminance) in thedisplay apparatus is adjusted so that the power to be consumed in thedisplay apparatus is controlled.

It is also possible to adjust the light emission amount (luminance), andthereby achieve the power control, by controlling only either one of thechangeover in emission type or the multiplying circuit coefficientdepending on the magnitude of the power prediction signal.

As described above, in the present invention, since a power predictionsignal is computed by using a coefficient representing a ratio of powerconsumptions necessary for data display of the individual colors, andsince the power prediction signal obtained in this way is used as aparameter, the automatic power control can be achieved more accuratelythan in the prior art method.

FIG. 9 shows a control characteristic showing variations in the powerprediction signal versus the light emission amount per unit area(luminance), where the horizontal axis represents the magnitude of thepower prediction signal and the vertical axis represents the lightemission amount per unit area (luminance). The controller 18, byadjusting the emission type or the multiplying coefficient in responseto the power prediction signal outputted from the adder 17, exerts itscontrol function so that the power consumed in the display apparatus isinhibited from becoming excessively large, by lowering the lightemission amount per unit area (luminance) as the power prediction signalincreases.

(Embodiment 2)

A second embodiment of the present invention is described. Thisembodiment shows another determination of the parameter KR, KG and KB ofEmbodiment 1. In this embodiment, these parameter KR, KG and KB aredetermined based on a ratio of areas of individual color phosphors,while it is based on the power ratio in the Embodiment 1.

FIG. 10 shows examples of the phosphor arrangement of a plasma displaypanel. In FIG. 10A, the stripe structure has a ratio of widths ofindividual color phosphors, WR:WG:WB=1.0:1.0:1.0, so that dischargeareas for R, G and B are of the same. Accordingly, a ratio of powers PR,PG and PB to be consumed for data display when the individual singlecolors are displayed on this panel is generally PR:PG:PB=1.0 1.0:1.0. Insuch a case, the ratio of he parameters KR, KG and KB with which the Raverage level, the G average level and the B average level is multipliedrespectively are determined as KR:KG:KB=1.0:1.0:1.0. The powerconsumption signal can be obtained by using such parameters KR, KG andKB.

Here is discussed a case in which the widths of individual colorphosphors are unbalanced with the view of improving the colortemperature as shown in FIG. 10B. In FIG. 4B, WR:WG:WB=1.0:1.0:1.4,where the width WB of the blue phosphor is broadened wider than those ofthe other two colors so that the color temperature of the panel isheightened. In this case, differences in phosphor width results indifferences in R, G and B discharge areas, and these differences arereflected in the consumed power for data display, with the result of aratio of PR:PG:PB=1.0:1.0:1.4, generally. In such a case, if the ratioof KR, KG and KB is set as KR:KG:KB=1.0:1.0:1.4, then the powerprediction signal can still be computed correctly.

Like this, the area of a phosphor is generally proportional to the powerconsumed for data display. Therefore, it is also possible to compute thepower prediction signal in a simplified manner by inputting a ratio ofphosphor areas as KR, KG and KB to the first multiplying circuit 14, thesecond multiplying circuit 15 and the third multiplying circuit 16 ofFIG. 1, respectively.

While the display apparatus with a plasma display panel (PDP) isdescribed above, this invention may also be applied to otheremission-type display apparatus such as a LED (Light Emission Diode)display apparatus, a field emission display (FED) and so on.

According to the present invention described above, the light emissionamount (luminance) in the display section of the display apparatus iscontrolled based on a power prediction signal which is obtained byweighting individual color average levels with coefficients representingthe power consumption ratio or phosphor area ratio, and then determininga sum of those weighted color average levels. Thus, there can beprovided a display apparatus which can be controlled in powerconsumption more accurately, as compared with the prior art method inwhich power consumption of the display apparatus is controlled by usingaverage luminance.

Although the present invention has been described in connection withspecified embodiments thereof, many other modifications, corrections andapplications are apparent to those skilled in the art. Therefore, thepresent invention is not limited by the disclosure provided herein butlimited only to the scope of the appended claims.

What is claimed is:
 1. A display apparatus comprising: an emission unitfor emitting light to display images; integrating circuits forintegrating input picture signals of R, G and B for a predeterminedperiod to output an average level of R signal, an average level of Gsignal and an average level of B signal, respectively; first, second andthird multiplying circuits for multiplying the R average level, the Gaverage level and the B average level by their respective parameters KR,KG and KB; a power prediction circuit for obtaining and outputting apower prediction signal indicative of amount of power expected to beconsumed on the emission unit by adding output signals from the first,second and third multiplying circuits together; a controller forreceiving said power prediction signal to output a control signal basedon a value of the received signal; and a brightness control circuit forcontrolling light emission amount of the emission unit per unit areaaccording to the control signal.
 2. The display apparatus according toclaim 1, wherein a ratio of parameters KR, KG and KB is determined to beequal to a ratio of powers consumed for display each color of red, greenand blue with same brightness.
 3. A display apparatus comprising: anemission unit for emitting light to display images; integrating circuitsfor integrating input picture signals of R, G and B for eachpredetermined period to output an average level of R signal, an averagelevel of G signal and an average level of B signal, respectively; first,second and third multiplying circuits for multiplying the R averagelevel, the G average level and the B average level by their respectiveparameters KR, KG and KB, respectively, the ratio of parameters KR, KGand KB being determined to be equal to a ratio of powers consumed fordisplay each color of red, green and blue with same brightness; a powerconsumption prediction circuit for obtaining and outputting a powerprediction signal indicative of amount of power expected to be consumedon the emission unit by adding output signals from the first, second andthird multiplying circuits together; a controller for receiving saidpower prediction signal to output a multiplying coefficient based on avalue of the received signal; a delay circuit for delaying the inputpicture signals of R, G and B to output the delayed picture signals DR,DG and DB, respectively; and fourth, fifth and sixth multiplyingcircuits for multiplying the delayed picture signals DR, DG and DB bythe multiplying coefficient, respectively.
 4. A display apparatus fordividing one field of picture signal into a plurality of subfieldsweighted respectively, and then displaying images of subfields insuperimposition on time region to realize gradation expression, saiddisplay apparatus comprising: an emission unit for emitting light todisplay images; R integrating circuit, a G integrating circuit and a Bintegrating circuit for integrating at least one field of input picturesignals of R, G and B to output an average level of R signal, an averagelevel of G signal and an average level of B signal, respectively; first,second and third multiplying circuits for multiplying the R averagelevel signal, the G average level signal and the B average level signalby parameters KR, KG and KB determined based on the ratio of powersconsumed on the emission unit to display each color of red, green andblue; a power prediction circuit for obtaining and outputting a powerprediction signal indicative of amount of power expected to be consumedon the emission unit by adding output signals from the first, second andthird multiplying circuits together; a controller for receiving thepower prediction signal to output a emission pulse control signal forselecting one of light emission types in response to a value of thereceived signal; a delay circuit for delaying the input picture signalsR, G and B to output the delayed picture signals DR, DG and DB,respectively; a picture signal-subfield associating circuit forreceiving the emission pulse control signal and the delayed picturesignals DR, DG and DB, and associating output signals from the delaycircuit with subfield structure of the light emission type based on theemission pulse control signal; and subfield pulse generator forreceiving the emission pulse control signal, and generating pulses inthe subfield structure corresponding to the light emission type based onthe emission pulse control signal, the pulses including at least one ofscanning pulses, sustaining pulses and erasing pulses.
 5. A displayapparatus for displaying images of subfields in superimposition on timeregion to display data with gradation, by dividing one field of picturesignal into a plurality of subfields weighted, said display apparatuscomprising: an emission unit for emitting light to display images; Rintegrating circuit, G integrating circuit and B integrating circuit forintegrating at least one field of input picture signals of R, G and B tooutput an R average level signal, a G average level signal and a Baverage level signal, respectively; first, second and third multiplyingcircuits for multiplying the R average level signal, the G average levelsignal and the B average level signal by respectively parameters KR, KGand KB obtained by a ratio of powers consumed for display each color ofred, green or blue, a power prediction circuit for obtaining andoutputting a power prediction signal indicative of power expected to beconsumed on the emission unit by adding output signals from the first,second and third multiplying circuits together; a controller forreceiving said power prediction signal to output a emission pulsecontrol signal and a multiplying coefficient according to a value of thereceived signal, said emission pulse control signal being available forselecting one of light emission types, said multiplying coefficientbeing available for equalizing gray scale level at a border of adjacentemission types, said multiplying coefficient being obtained based onsaid power prediction signal from the controller; a delay circuit fordelaying the input picture signals of R, G and B to output delayedpicture signals DR, DG and DB, respectively; fourth, fifth and sixthmultiplying circuits for multiplying the delayed picture signals DR, DGand DB by said multiplying coefficient for collecting gray scale levelso as to equalize gray scale level between adjacent emission types atchangeover point of those emission types, respectively; a picturesignal-subfield associating circuit for receiving the emission pulsecontrol signal and the signals of the fourth, fifth and sixthmultiplying circuits as inputs, and associating the received signalsfrom the fourth, fifth and sixth multiplying circuits with subfieldstructure of a light emission type responsive to the emission pulsecontrol signal; and subfield pulse generator for receiving the emissionpulse control signal, and generating pulses including scanning,sustaining, erasing pulses with said subfield structure of the lightemission type responsive to the emission pulse control signal.
 6. Thedisplay apparatus according to claim 1, wherein a ratio of theparameters KR, KG and KB is equal to a ratio of area of phosphors foreach color of red, green and blue.